Easy DIY Relay 109 repair!

n1das

TDIClub Enthusiast, Veteran Member
Joined
Jun 11, 2002
Location
Nashua, NH, USA
TDI
2014 BMW 535xd ///M-Sport, 2012 BMW X5 Xdrive35d, former 3x TDI owner
A coworker of mine recently experienced the classic Relay 109 failure in his 2000 Jetta TDI. He still had the original Relay 109 and replaced it with the updated Relay 109 and his car is running fine again. TDIclub played a big part in educating him about the classic Relay 109 failure in older VWs.

Meanwhile he decided to open up the old relay and analyze the failure. The relay contacts appeared OK under a microscope. The contacts actually were not burned or pitted at all and no metal migration from one contact to the other...still good. While looking under the microscope we also took a look at the solder connections on the PCB and found a few that looked suspect. The pics below say it all....

Relay 109....


A few solder joints on the PCB looked suspicious.....


The large solder joint to pin "30" was cracked and broken, making intermittent contact:


Here's another view of the same (cracked and broken) solder connection:


We also found one of the smaller solder connections to be cracked and broken. This connection feeds one side of the
relay coil. Intermittent contact here would cause the relay to drop out and kill power to the car. :eek:


After re-soldering all connections on the PCB, he now has a spare working Relay 109. :cool:
 
Last edited:

n1das

TDIClub Enthusiast, Veteran Member
Joined
Jun 11, 2002
Location
Nashua, NH, USA
TDI
2014 BMW 535xd ///M-Sport, 2012 BMW X5 Xdrive35d, former 3x TDI owner
This has been reported in the past, although not with such detailed photos!!

Thanks for sharing!!!!

Yuri
It should be a big help for the large influx of newbies we've had in recent years. A lot are buying used TDIs and probably unaware of the classic Relay 109 failure in older TDIs.

We had access to a good stereo microscope at the time and I used my cell phone camera to grab the pics thru the microscope. :cool:
 

where2

Veteran Member
Joined
Oct 29, 1999
Location
North Palm Beach, FL, USA
TDI
One '13 JSW_TDI & One '04 Variant_TDI
Re-hashed or not, I'll take the cold solder joint info and tuck it away for a rainy day. My dad taught me to look for those sorts of problems when I was little.

Years ago, when my wife and I were just dating, her Sony home stereo tuner had an intermittent front display screen that had been driving her nuts. One evening, I took it apart and found several cracked cold solder joints in the wiring to the display. It still works flawlessly today, after 10+ years of marriage, and a few minutes late one night with a soldering iron.

(I'm the son of an electronics technician, my dad fixed my wife's 1938 Zenith Shutterdial tube radio... Yes, 74 years old and it still works!)
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Yeah, the cracked solder joints is why that the "ugly" 109 Ghost can show it's face today but be just fine tomorrow only to let you down the next day!

Yep, the photos should be helpful to the Newbies!
 

erbilabuc

Veteran Member
Joined
Jan 12, 2011
Location
Jacksonville, nc
TDI
2003 Green Jetta wagon
correct me if I am wrong but cant this problem be bypassed with the 109 relay if you take a wire directly from positive side of battery to fuel shut off valve on injection pump?
I ask because I am waiting for the 2 109 relays i ordered to arrive.

thanks
 

n1das

TDIClub Enthusiast, Veteran Member
Joined
Jun 11, 2002
Location
Nashua, NH, USA
TDI
2014 BMW 535xd ///M-Sport, 2012 BMW X5 Xdrive35d, former 3x TDI owner
correct me if I am wrong but cant this problem be bypassed with the 109 relay if you take a wire directly from positive side of battery to fuel shut off valve on injection pump?
I ask because I am waiting for the 2 109 relays i ordered to arrive.

thanks
I don't think so since the ECU needs to be powered and power to the ECU is supplied thru Relay 109.

One thing I noticed is the terminals "85", "87", and "30" are the same labeling and physical locations as on a popular 12V 30A lighting relay I can buy at my local RadioShack store. I'm curious to know if it is interchangeable with a genuine Relay 109 or not.
 

Abacus

That helpful B4 guy
Joined
Nov 10, 2007
Location
Relocated from Maine to Prescott, AZ
TDI
Only the B4V left
Hmmm, interesting. When I had my 109 problem, I was able to jumper it to the battery and get it running. But now that I think about it, it was a wiring issue after the ECU, which had power. So perhaps I am wrong.

Maybe I'll go pull my 109 relay and jumper the car, to see if it starts.
 
Last edited:

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
109 functions

correct me if I am wrong but cant this problem be bypassed with the 109 relay if you take a wire directly from positive side of battery to fuel shut off valve on injection pump?
I ask because I am waiting for the 2 109 relays i ordered to arrive.

thanks
The answer is Yes in part!

Here are the Relay 109 Circuits:

Relay 109 and associated Circuits Located at Position 12 in the upper relay panel.

Relay 109 is identified as J317, Power Supply from Terminal B+ (hot at all times) with power activation from the ECU when the key is in the ON position

Power Circuit to Relay 109
1. Power (6.0 size red wire) comes from Fuse S176 (110amps) at the plastic box on battery to Threaded Connection 500 at the relay plate -1- (30).
2. From the Relay Plate, at Connection 501 the power (6.0 size red wire) goes to Splice A98
3. From Splice A98, the power (4.0 size red wire) goes to Terminal 2/30 of Relay 109


Relay Circuit (activated when the Ignition is turned on)
1. Connection 9/85 goes to Blue Connector T10h/8 on to ECU at T121/18

Power Circuit away from Relay 109
1. Power away from Relay 109 is via 4.0 Blue Wire to Splice A71
2. At Splice A71, there are three circuit branches (A, B, & C, my terminology)
Circuit - A. 1.5 Wire goes to Fuse 34 (10 amp)
Circuit - B. 4.0 Wire goes to Fuse 32 (30 amp)
Circuit - C. 1.5 Wire goes to Fuse 43 (10 amp)
 
Circuit A (with two branches) ........ engine operation functions
From Fuse 34
goes to Splice 100, first branch provides power to: MAF (G70), Wastegate Bypass Regulator Valve (N75), EGR Vacuum Solenoid Valve (N18) and Change-over Valve for intake manifold flap (N239) Note: tied to this same circuit, is another circuit that comes from a 1.0 size wire from connection 6/87 of the GP relay. The second branch , Splice 100, goes to the 14 Pin Connector at T14a/6 on to Cold Start Injector (N108)

Circuit B (with two branches)
From Fuse 32 goes to Splice B168, first branch (4.0 wire) goes to Brown Connector point T6/4 on to splice D74 and provides power to: ECU at T121/1 and T121/2 via the two branches at Splice D74. The second branch goes to the 10 pin connector at the Injection Pump (G149), connection T10f/5

Circuit C (with three branches)
From Fuse 43 goes to Splice A155 , the first branch goes to Clutch Vacuum Vent Switch (F36). The second branch (page 10) goes to Brown Connector at T6/6 with double wire of which one goes to a 53 Relay J359 for Low Heat Coolant GP and the other goes to the Positive Crankcase Ventilation Heating Element (N79). The third branch goes to the Brake Vacuum Vent Valve Switch (F47)


Personally, I wouldn't be doing any wire jumping!
 

Abacus

That helpful B4 guy
Joined
Nov 10, 2007
Location
Relocated from Maine to Prescott, AZ
TDI
Only the B4V left
Hmmm, interesting. When I had my 109 problem, I was able to jumper it to the battery and get it running. But now that I think about it, it was a wiring issue after the ECU, which had power. So perhaps I am wrong.

Maybe I'll go pull my 109 relay and jumper the car, to see if it starts.
I just went and checked it, and the answer is yes, if you leave everything else alone. I pulled my 109 relay completely out of the car, simulating it was dead. Then I found:

If you remove the black/white wire from the top of the N109 valve on the IP, then jumper from the battery to the N109 valve, the car will not run.

However: if you leave that wire in place and jumper from the battery to N109, it will run.

So the car will run if your N109 relay dies and you just run a jumper from the battery to the top of the N109 valve, even if the N109 relay isn't present.

This is good to know if you have a N109 relay that dies suddenly and you don't have a spare, or if your relay is good and your wiring chafes through, like what happened to mine and an A3 locally.

Not sure I'd run it this way too long since I believe power will be backfed into the ECU (allowing it to work), and I'm not sure of what damage that might do.
 
Last edited:

erbilabuc

Veteran Member
Joined
Jan 12, 2011
Location
Jacksonville, nc
TDI
2003 Green Jetta wagon
Yeah ill just stop tryimg to start it and wait for the relays to come in. I live in hawaii so im desperate to car running and dealer wants to replace FIP and engine rebuild. No thanks
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
I just went and checked it, and the answer is yes, if you leave everything else alone. I pulled my 109 relay completely out of the car, simulating it was dead. Then I found:

If you remove the black/white wire from the top of the N109 valve on the IP, then jumper from the battery to the N109 valve, the car will not run.

However: if you leave that wire in place and jumper from the battery to N109, it will run.

So the car will run if your N109 relay (109 Relay, not N109 Relay) dies and you just run a jumper from the battery to the top of the N109 valve, even if the N109 relay (109 Relay, not N109 Relay) isn't present.

This is good to know if you have a N109 relay (109 Relay, not N109 Relay)that dies suddenly and you don't have a spare, or if your relay is good and your wiring chafes through, like what happened to mine and an A3 locally.

Not sure I'd run it this way too long since I believe power will be backfed into the ECU (allowing it to work), and I'm not sure of what damage that might do.


This is good information to know. However, what you have described involves backfeeding current as indicated. The Fuel Cut-off valve (N109) has only one circuit which goes directly to the ECU at pin 120. Knowing how many other items that "pull current" by jumping via the N109 valve concerns me. (Examples: they are all listed in my other post)

The reason it didn't work jumping only to the wire and not to the valve was because the valve needs current to open.

Notice above in the quote, for those who read, Abacus inadvertently used N109 Relay and Relay 109 interchangeably. They are two different things. In fact N109 (fuel cut-off valve) is not a relay, its a solenoid cut-off valve.

Lastly, if you will notice in the Post I made above, the circuits going to Relay 109 are heavy wires.............. do you think that the single tiny pin at 120 on the ECU can stand the current draw? If you notice very close in the info I posted, there are three major circuits (all fused separately) that have sub-circuits.........

I would not jump from battery to the N109 fuel cut-off valve under any circumstances!
 
Last edited:

Abacus

That helpful B4 guy
Joined
Nov 10, 2007
Location
Relocated from Maine to Prescott, AZ
TDI
Only the B4V left
My apologies for the confusion regarding N109 and 109 relay, I was typing fast to try and avoid the afternoon rush.

"The reason it didn't work jumping only to the wire and not to the valve was because the valve needs current to open."

But the valve did open when I jumped to it since its grounded off the engine. I distinctly heard it click. The power was not back feeding to the ECU so it would not run. The engine definitely got fuel as evidenced by the abnormal start after I reconnected everything properly.

Thanks for the insight on this.
 
Last edited:

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
My apologies for the confusion regarding N109 and 109 relay, I was typing fast to try and avoid the afternoon rush.

"The reason it didn't work jumping only to the wire and not to the valve was because the valve needs current to open."

But the valve did open when I jumped to it since its grounded off the engine. I distinctly heard it click. The power was not back feeding to the ECU so it would not run. The engine definitely got fuel as evidenced by the abnormal start after I reconnected everything properly.

Thanks for the insight on this.

I've generally had too much Canadian Mist when I mix up things like that.........:D
 

Abacus

That helpful B4 guy
Joined
Nov 10, 2007
Location
Relocated from Maine to Prescott, AZ
TDI
Only the B4V left
What? Sacrilege! A Kentuckian drinking Canadian Mist? Oh, the horror! Coming from the patron state of drinking, you choose something from out of country?

That's it, turn in your bottle and step away. :D

I'll give you my address so you can send it to me for proper disposal.
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
What? Sacrilege! A Kentuckian drinking Canadian Mist? Oh, the horror! Coming from the patron state of drinking, you choose something from out of country?

That's it, turn in your bottle and step away. :D

I'll give you my address so you can send it to me for proper disposal.

Don't you just love it?

Well, actually, my credenza has a few bottles of good Kentucky Bourbon in it, as well as a jar or two of smooth shine (not rot gut).....from my secret source!:D
 

Abacus

That helpful B4 guy
Joined
Nov 10, 2007
Location
Relocated from Maine to Prescott, AZ
TDI
Only the B4V left
I know it's OT, but my brother lives in Quality (around Morgantown), and I had some local shine when I visited last, it was simply amazing and some of the best sipping stuff I've ever had. Normally I can't do the hard stuff anymore since being burned on it stationed overseas in the Army, but this really was good. I envy you guys, but your summer weather is just too hot for this northern boy.

And now back to our regularly scheduled 109 relay thread.... :D
 

wmgeorge

Veteran Member
Joined
Jun 22, 2012
Location
Central Iowa
TDI
2000 New Beetle GLS 1.9L TDI
So relay 109 is a "special" relay not a standard plug in relay with either a 12V or 5V coil?

One thing I noticed is the terminals "85", "87", and "30" are the same labeling and physical locations as on a popular 12V 30A lighting relay I can buy at my local RadioShack store. I'm curious to know if it is interchangeable with a genuine Relay 109 or not.
 
Last edited:

Alchemist

Veteran Member
Joined
Nov 3, 2007
Location
Lethbridge, Alberta
TDI
'04 ALH Golf
There is one terminal missing from the 109 else it would be an ordinary relay. There is an internal connection from 30 to 86, which explains why this terminal is not on the relay. The ECU grounds terminal 85 and the relay operates because of the internal connection.
 

wmgeorge

Veteran Member
Joined
Jun 22, 2012
Location
Central Iowa
TDI
2000 New Beetle GLS 1.9L TDI
There is one terminal missing from the 109 else it would be an ordinary relay. There is an internal connection from 30 to 86, which explains why this terminal is not on the relay. The ECU grounds terminal 85 and the relay operates because of the internal connection.
Just checking. I know a lot of special relays are just relabeled standard plug in relays. I have a lot of those in my inventory. How much do these 109 relays cost and where do you buy them?
 

firehawk618

Veteran Member
Joined
Aug 20, 2003
Location
Marysville, WA
TDI
2011 Golf TDI, 2dr, M6, Stock
Great post.

Just a FYI for anyone, this is common on all kinds of relays. Honda main relay, saab headlight relay, etc etc.

When a relay is suspect it seems more often than not repairing the poor solder joints fixes the issue.
 
Top